This invention relates to a recording medium cartridge having a recording medium such as a magnetic tape, a flexible disc, a hard disc, an optical disc or the like housed or received therein, and more particularly to a recording medium cartridge such as a video tape cassette, an audio tape cassette, a disc cartridge or the like.
A recording medium for recording information or data thereon is generally apt to cause dust or the like to adhere thereto and be readily damaged. Also, the recording medium is adversely affected by a variation in temperature and required to exhibit convenience in handling. In view of the situation, the record medium is typically charged in a recording and/or reproducing unit while being received in a casing made of a synthetic resin material or in the form of a recording medium cassette or cartridge.
In the conventional recording medium cartridge, an upper casing member and a lower casing member each made of acrylonitrile-butadiene-styrene (ABS) resin, polycarbonate (PC) resin, polystyrene (PS) resin or the like are joined together by welding to provide the casing. The resins described above each permit welding between the upper casing member and the lower casing member to be satisfactorily carried out, however, they cause the casing to be readily scraped or ground to produce tailings and/or dust, which then adhere to a head of a recording and/or reproducing unit, its spindle, and/or the recording medium, leading to dropout and/or permanent error of data stored in the recording medium. Also, the casing is deteriorated in sliding properties to a degree sufficient to cause handling of the cartridge to be deteriorated.
Those skilled in the art would consider that the above-described problems are solved by forming the casing of crystalline resin which inherently exhibits satisfactory lubricous or sliding properties. Unfortunately, the crystalline resin is elastic and readily absorbs thermal or heat energy, to thereby render welding between the upper casing member and the lower casing member highly difficult. This causes conditions for the welding and a configuration of the welding to be substantially restricted, to thereby fail to increase productivity of the recording medium cartridge.
Referring now to FIG. 1, such a conventional recording medium cartridge as described above is illustrated. The recording medium cartridge shown in FIG. 1 is in the form of a video tape cassette. More particularly, in the conventional recording medium cartridge or video tape cassette, a casing for receiving a recording medium or a magnetic tape therein comprises an upper casing member 100 and a lower casing member 102 joined to each other by welding. For this purpose, the upper and lower casing members 100 and 102 are provided on surfaces thereof mating with each other with projections 104 for welding, respectively. Also, the upper and lower casing members 100 and 102 are formed on the projections 104 or surfaces of peripheral walls thereof mating with or opposite to each other with ribs 106. Then, the upper and lower casing members 100 and 102 are joined together through the projections 104 and/or ribs 106 by means of a welding horn 108. Thus, welding between both casing members 100 and 102 is carried out at positions centrally located in a vertical direction of the casing. Unfortunately, the positions are defined so as to be away by a distance as large as 10 to 14 mm from an outer surface of the casing member against which the welding horn 108 is abutted for welding. This fails to permit the welding to be successfully carried out. In particular, when the welding is carried out between the outer peripheral mating surfaces of the casing members, squeeze-out or extrusion of the resin material for the casing being melted occurs during and/or after the welding, to thereby deteriorate an appearance of the casing and therefore the cartridge. Also, when both casing members and therefore the projections 104 for welding are made of crystalline resin, a large amount of energy is required to melt the projections. Unfortunately, this often causes portions of both casing members other than the projections 104 to be concurrently melted together with the projections 104, resulting in further deteriorating the appearance.
Further, as will be noted from the foregoing, the casing of the conventional recording medium cassette or video tape cassette is increased in strength in a vertical direction thereof, however, it is decreased in strength or rigidity in longitudinal and lateral directions thereof; therefore, torsion applied to the casing or shock applied to the casing due to dropping of the cartridge, or the like causes separation of the upper and lower casing members from each other.
The present invention has been made in view of the foregoing disadvantages of the prior art.
Accordingly, it is an object of the present invention to provide a recording medium cartridge which is capable of being extensively increased in sliding properties and welding properties, to thereby facilitate the handling and increase the productivity.
It is another object of the present invention to provide a recording medium cartridge which is capable of permitting a welding operation to be smoothly accomplished with high efficiency.
It is a further object of the present invention to provide a recording medium cartridge which is capable of permitting a welding operation to be satisfactorily carried out to a degree sufficient to prevent an appearance of the cartridge from being deteriorated.
It is still another object of the present invention to provide a recording medium cartridge which is capable of carrying out a welding operation to be carried out while reducing loss of energy for welding to decrease vibrational energy required for welding.
It is yet another object of the present invention to provide a recording medium cartridge which is capable of exhibiting mechanical strength sufficient to permit the cartridge to endure torsion applied thereto, shock applied thereto due to dropping of the cartridge, or the like.
It is a still further object of the present invention to provide a recording medium cartridge which is capable of exhibiting high safety and reliability and increased bonding strength while keeping the structure simplified and the manufacturing cost reduced.
The term xe2x80x9crecording medium cartridgexe2x80x9d used herein, as will be readily understood to those skilled in the art, means a recording medium operated in a recording and/or reproducing unit while being received in a casing, such as a video tape cassette, an audio tape cassette, a disc cartridge and the like.
In accordance with the present invention, a recording medium cartridge is provided. The recording medium cartridge of the present invention includes a casing in which a recording medium is received. The casing comprises an upper casing member and a lower casing member jointed to each other. The upper and lower casing members are made of crystalline resin and jointed together by welding. The crystalline resin has a filler which permits the crystalline resin to exhibit improved welding properties incorporated therein.
The present invention constructed in the manner described above permits transmission of energy from an ultrasonic welding horn to the upper and lower casing members to be satisfactorily carried out to improve welding between both casing members, so that both casing members may be safely and effectively welded together. Also, the casing exhibits good sliding properties because of being formed of crystalline resin, to thereby effectively prevent damage to the recording medium in the casing and ensure charging of the cartridge in a recording and/or reproducing unit. Thus, the present invention effectively prevents scraping of the cartridge and dropout and permanent error of information or data stored in the recording medium.
In a preferred embodiment of the present invention, the recording medium cartridge may be in the form of a tape cassette, wherein the upper and lower casing members are joined through welded surfaces thereof to each other, and the welded surfaces are defined in a manner to be spaced by a distance corresponding to one eighth to one quarter as large as a total thickness of the casing from a surface of the casing with which a welding horn is kept contacted during welding.
In such construction, application of vibrational energy from the welding horn to the upper casing member permits the welded ribs to be melted to integrally join both casing members to each other. This results in preventing an appearance of the cartridge due to extrusion of the resin material from the casing from being deteriorated, reducing loss of energy output from the welding horn, facilitating and improving the welding operation, and reducing vibrational energy required for the welding.
In another preferred embodiment of the present invention, the upper and lower casing members are joined to each other through welded portions thereof. The welded portions comprise annular bosses provided on the upper and lower casing members so as to positionally correspond to each other. The bosses of one of the casing members each are formed therein with a central boss so as to project therefrom, which is fitted in corresponding one of the bosses of the other casing member.
Such construction permits the casing and therefore the cartridge to exhibit rigidity sufficient to endure torsion applied to the cartridge and shock applied thereto by dropping of the cartridge.